DataTable使用

using System;
using System.Data;
using System.Data.SqlClient;

namespace Chapter12
{
    class SchemaTable
    {
        static void Main(string[] args)
        {
            // connection string
            string connString = @"
                            server = .;
                            integrated security = true;
                            database = northwind
                         ";

            // query 
            string sql = @"
                        select
                           *
                        from
                           employees
                     ";

            // create connection
            SqlConnection conn = null; 
            SqlDataReader rdr = null;
            try
            {
                conn = new SqlConnection(connString);
                conn.Open();

                SqlCommand cmd = new SqlCommand(sql, conn);
                rdr = cmd.ExecuteReader();

                // store Employees schema in a data table
                //首先调用DataTable.GetSchemaTable()函数
                //把执行的结果放置到DataTable中。
                DataTable schema = rdr.GetSchemaTable();

                // display info from each row in the data table.
                // each row describes a column in the database table.
                //两个foreach循环，先是行循环再是列循环
                foreach (DataRow row in schema.Rows)
                {
                    foreach (DataColumn col in schema.Columns)
                        Console.WriteLine(col.ColumnName + " = " + row[col]);
                    Console.WriteLine("----------------");
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("Error Occurred: " + e);
            }
            finally
            {
                rdr.Close();
                conn.Close();
            }
        }
    }
}

//所有代码来自书籍《Begining C# Databases From Novice to Professional》